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Systematic Micaceous Minerals

Saturday, 29 December 2012 09:00 PM

Not all micaceous looking minerals fall in the MICA group of phyllosilicate minerals. Many of the other silicates appear micaceous but are not. We'll have a look at some of these minerals and hopefully explain the difference. Take a look at our article on Mica and Other Micaceous Minerals.

Norrishite

#PD34818
Locality
Hoskins Mine, Grenfell, Forbes Co., New South Wales, Australia 
Formula
KLiMn3+2[O2| Si4O10
Availability
Sold
Size
2 x 1 x 1 cm - Thumbnail 
Special Info
Type Locality 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal with Lithium and trivalent Mn.

Occurs as shiny black flakes to 1.5mm which are translucent to opaque. In rock forming oxidized, Mn-rich silicate rock (Bernard & Hyrsl). Mindat list 4 localities worlwide.


Norrishite

Formula
KLiMn3+2Si4O12 
Crystal System
Monoclinic 
Crystal Habit
Foliated, Massive 
Cleavage
Perfect, None, None 
Luster
Sub Metallic 
Color
brownish black, black 
Streak
light brown 
Class
Monoclinic - Prismatic 
Hardness
2.5 
Collection
Phillips Collection
Special Info
Type Locality
SOLD
Phlogopite - PD34671
Phlogopite - PD34671

Phlogopite

#PD34671
Locality
Kola Peninsula, Russia 
Formula
KMg3(Si3Al)O10(OH)2 
Availability
Sold
Size
6 x 5.5 x 0.4 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. End member. Ordinary (True or Common) Mica - Trioctahderal with Mg at the (M) positions, K as (I), and OH as (A). Mg end member of Biotite-Phlogopite series.

Occurs sometimes as primary mineral in igneous rocks, mainly ultrabasic, in Leucite-pyroxene rock called "Wyomingite", serpentenized dunnites, altered kimberlites, alkaline ultrabasic rocks in Kola, Russia.

Excellent cleaved crystal.


Phlogopite

Formula
KMg3(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Micaceous, Scaly, Lamellar 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
brown, gray, green, yellow, reddish brown 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-2.5 
Collection
Phillips Collection

Phlogopite

#PD34686
Locality
Iron mine, Kovdor Massif, Kola Peninsula, Russia 
Formula
KMg3(Si3Al)O10(OH)2 
Availability
Sold
Size
4 x 3.5 x 0.2 cm - Miniature 

Phyllosilicate - Monoclinic - Mica group member. End member. Ordinary (True or Common) Mica - Trioctahderal with Mg at the (M) positions, K as (I), and OH as (A). Mg end member of Biotite-Phlogopite series.

Occurs sometimes as primary mineral in igneous rocks, mainly ultrabasic, in Leucite-pyroxene rock called "Wyomingite", serpentenized dunnites, altered kimberlites, alkaline ultrabasic rocks in Kola, Russia.

Nice green crystal plate.


Phlogopite

Formula
KMg3(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Micaceous, Scaly, Lamellar 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
brown, gray, green, yellow, reddish brown 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-2.5 
Collection
Phillips Collection

Phlogopite

#PD32847
Locality
Balmat, St. Lawrence Co., New York, United States 
Formula
KMg3(Si3Al)O10(OH)2 
Availability
Sold
Size
6 x 4 x 2 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. End member. Ordinary (True or Common) Mica - Trioctahderal with Mg at the (M) positions, K as (I), and OH as (A). Mg end member of Biotite-Phlogopite series.

Occurs sometimes as primary mineral in igneous rocks, mainly ultrabasic, in Leucite-pyroxene rock called "Wyomingite", serpentenized dunnites, altered kimberlites, alkaline ultrabasic rocks in Kola, Russia.

Scaly mass.


Phlogopite

Formula
KMg3(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Micaceous, Scaly, Lamellar 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
brown, gray, green, yellow, reddish brown 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-2.5 
Collection
Phillips Collection

Polylithionite

#PD34673
Locality
Mont Saint-Hilaire, Rouville Co., Quebec, Canada 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
4.5 x 4 x 1 cm - Miniature 

Phyllosilicate - monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal.

Nice rosettes of psedohexagonal crystals to 2.5cm across.


Polylithionite

Formula
KLi2AlSi4O10F2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal, Tabular, Scaly 
Cleavage
Perfect, None, None 
Luster
Pearly 
Color
bluish, colorless, violet, greenish, pearl white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-3 
Collection
Phillips Collection

Polylithionite

with Aegerine - #PD34811
Locality
Ilimaussaq complex, Narsaq, Kitaa prov., Greenland 
Formula
K(Li, Al)2[(F, OH)2|(Si, B)4O12 
Availability
Sold
Size
8 x 5.5 x 2.5 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. End member. Ordinary (True or Common) Mica - Trioctahderal with lithium and aluminum in the (M) positions, Si and boron in the (T) positions, F>OH in the (A) position and K as the Interlayer cation.

Occurs as tabular crystals with hexagonal outline, also scaly, fine grained, white, gray, pale green, pale pink and violet. Can be fluorescent green. Typically found in alkaline syenites and their pegmatites including MSH and Ilimaussaq.

This is a larger specimen with Aegerine and a Copenhagen label.


Polylithionite

Formula
KLi2AlSi4O10F2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal, Tabular, Scaly 
Cleavage
Perfect, None, None 
Luster
Pearly 
Color
bluish, colorless, violet, greenish, pearl white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-3 
Collection
Phillips Collection

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